Variable-delivery positive displacement pump



April 18, 1961 J. A. POPE 2,980,024

VARIABLE-DELIVERY POSITIVE DISPLACEMENT PUMP Filed March 3, 1958 United States Patent() 2,980,024 v VARIABLE-DELIVERYPPOSITIVE DISPLACEMENT 4 Claims. (Cl. 103-37) This invention comprises improvements in or relating to liquid pumps and has for an object to provide a variabledelivery positive-displacement pump whereof the delivery can be varied readily during operation ofthe pump.

According to the presentl invention, a variable-delivery positive-displacement liquid pump comprises a pump body having an internal bore, a pump cylinder having an outlet at one end and an inlet at a point intermediate its ends,

which cylinder is slidably accommodated within the bore in the pump body and bears at its outlet end against an yabutment member adjustably mounted preferably threaded in the pump body to permit adjustment of the abutment member lengthwise of the body, and aV pump piston which is reciprocated in the cylinder towards and away from the outlet and is arranged in its stroke to cover and uncover the inlet to the cylinder. In operation the liquid pressure within the cylinder maintains the cylinderin abutment with the abutment member and thus by adjustingtlie abutment member,. the point in the stroke of the piston at which the piston just covers the inlet can be varied so varying the delivery of the pump.

If desired, locking means may be provided whereby the pump cylinder may be locked to the abutment member during normal operation, the locking means being released when lit is desired 'to adjust the pump delivery. In this case, the cylinder is reqiure'd to be maintained against the abutment member by fluid pressure only when the locking means is released.

In one preferred form, the abutment member is an annular plug threaded in the end of the body adjacent the outlet end of the cylinder, the outlet is a union member rigid with the cylinder and projecting through the plug to externally ofthe body, and the locking means is a lock threaded onthe projecting portion of the union member and adapted when tightened to engage the plug and to draw the cylinder against the plug. Also, the abutment member has a portion projecting externally of the body and engageable by a tool to permit its adjustment during operation of the pump.

The invention also comprises pumping apparatus comprising a pair of like circular eccentrics carried on a driven spindle with their centres'oifset from the spindle axis by equal amount on opposite sides of the spindle, and a pair of pumps as above set forth disposed one on each side of the spindle, the pistons of the pumps being reciprocated each by a corresponding one of the eccentrics.

One construction of pumping apparatus incorporating pumps of this invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is an elevation of the pumping apparatus with parts in section,

Figure 2 is a plan view of the pumping apparatus and Figure 3 is a section through a pump showing details of the construction.

Referring to Figures 1 and 2, the pumping apparatus comprises a base 10 wherein is mounted an electric motor 11 driving a ily-wheel 12 through a belt 13. The y- Patented Apr. 18, 1961 'ice wheel spindle 12a has secured on it a pair of circular eccentrics 14 each of which operates a pump 15. The eccentrics are alike and are set with their centres offset by equal amounts on opposite sides of the axis of spindle 12a, and the pumps 15 are mounted on a frame 16 secured on the base 10, the pumps being respectively on each side of the spindle 12a. The pumps 15 thus operate in synchronism. l

Referring now to Figure 3, each pump 15 comprises a pump body 17 of cylindrical form with avboss 18 at one end which projetcs through a hole in the frame 16 and receives a retaining nut 19 by which the pump body 17 is secured to the frame 16. The body 17 has a bore housing a pump cylinder 20. The cylinder 20 has an outlet union- 23 threaded into its end remote from the frame 16 and is formed between its ends with two inlet ports 24. Liquid is fed to each inlet port 24 through a flexible inlet pipe 26 which is secured to a bored plug 35 which extends through and slides in a slot 25 inthe body 17 and which is threaded into the port 24.

of the body 17 remote from the frame 16, encircles the union 23 andY is normally locked to the cylinder 20 by being gripped between a flange 23a on the union 23 and alock nut 29 threaded on to the union 23. The plug 28 has a capstan end 28a to enable it to be rotated by means of a tommy bar or other suitable' tool. l Eachpurnp 15 also comprises 4a piston 30 working in the cylinder 20 under control of the associated eccentric 14 which effects the delivery stroke througha plunger 31V and a spring 32 which eiects the return stroke. The spring 32 at one end abuts a plate 33 secured on the end of the piston 30 and at its other end abuts a ring 34 secured tothe body 17. The ring 34 also serves to limit the adjustment of the cylinder 20 to the right as viewed in the drawing so that the cylinder cannot take upa position in which the`inlet portV 24 is never uncovered in the travel of the piston 30.

In operation, the piston 30 is reciprocated with a xed length of stroke under control of the eccentric 14 and the spring 32. During the intial part of the delivery stroke, the port 24 is uncovered so that the liquid is not pressurized. However, when in moving to the left, the piston 30 moves beyond the position in which it just covers the port 24, a quantity of liquid is trapped in the cylinder 20 and further movement to the left of the piston delivers the trapped liquid under pressure through the outlet union 23.

The quantity o'f liquid delivered at each stroke is varied by adjusting the plug 28 to vary the position of port 24 relative to the piston and this can be done while the pump is working. This adjustment is effected by releasing the lock nut 29 and rotating the plug 28 by means of the tommy bar or like tool. If the pump is working, the ange 23a is maintained in abutment with the plug 28 by the pressure within the cylinder even though the lock nut 29 is released.

The pumping apparatus as above described may be employed in connection with test apparatus as described in United States application Serial No. 718,679, led on March 3, 1958, by Pope et al.,.and in this case, if desired, means may be provided to adjust the position of the plug 28 cyclically so that the delivery of the pump 15 is varied cyclically to obtain a varying pressure eiect in the test apparatus.

I claim:

1. A variable-delivery positive-displacement liquid pump comprising a pump body having an axial bore, a pump cylinder slidable axially within the bore of the body,

, said pump cylinder having an internal cylinder bore open at one end, an inlet to the cylinder bore intermediate its ends and an youtlet at its opposite end, and said pump cylinder also having an abutment surface at said opposite end facing axially away from said. one end, an abutmentmember mounted in said pump body axially in line with the cylinder and beyond the outlet end thereof, said abutment member having an abutment face facing towards andy cooperating in axial abutment with the abutment surface of the pump cylinder to limit sliding of the pump cylinder in one direction, said abutment member being adjustable in the pump body axially of the bore to vary the position of the pump cylinder, said abutment member having a portion projecting-externally of the pump body and engageable by a tool to permit its adjustment axially of the pump body during operation of the pump, a pump piston extending axially into said pump cylinder through the open end thereof, andvdrive meansimparting to the piston a stroke to cover and uncover the inlet.

2. A variable-delivery positive-displacement liquid pump according to claim 1, comprising also locking means adapted to hold the cylinder in abutment with the abutment member, said locking means being releasable to permit adjustment of the abutment member in said body.

3. A variable-delivery positive-displacement liquid pump comprising a pump body having an axial bore, a pump cylinder slidable axially within the bore of the body, said pump cylinder having an internal cylinder bore open at one end, an inlet to the cylinder bore intermediate its ends and an outlet member at its opposite end, and said pump cylinderalso having an abutment surface at said opposite end facing axially away from said one end, an abutment member in the form of an annular plug threaded in the end ofthe body adjacent the outlet endof the cylinder, the outlet member being a union member rigid with the cylinder and projecting through the plug externally of the body, said abutment member having an abutment face cooperating with the abutment surface of the pump cylinder to limit sliding of the pump cylinder in one direction, said abutment member being adjustable in the pump body axially of the bore to vary the limit of sliding of the pump cylinder, a lock nut threaded on the projecting portion of the union member and adapted when tightened to engage the plug and to draw the cylinder against the plug, said lock nut being releasable to permit adjustment of the abutment member in the body, a pump piston extending axially into said pump cylinder through the open end thereof, and drive means imparting to the piston a stroke to cover and uncover the inlet.

4. A Variable-delivery positive-displacement liquid pump comprising a pump body having an axial bore, a pump cylinder slidable axially within the bore of the body, said pump cylinder having an internal cylinder bore open at one end, an inlet to the cylinder bore intermediate its ends and an outlet member at its opposite end, and said pump cylinder also having an abutment surface at said opposite end facing axially away from said one end, an abutment member in the form of an annular plug threaded in the end of the body adjacent the outlet end of the cylinder, the outlet member being a union member rigid with the cylinder and projecting'through the plug externally of the body, said abutment member having an abutment face cooperating with the abutment surface of the pump cylinder to limit sliding of the pump cylinder in one direction, said abutment member being adjustable in the pump body axially of the bore to vary the position of the pump cylinder, a pump piston extending axially into said pump cylinder through the open end thereof, and drive means imparting to the piston a stroke to cover and uncover the inlet.

References Cited in the file of this patent UNITED STATES PATENTS 1,724,156 Winton Aug. 13, 1929 2,337,510 Trevaskis Dec. 21, 1943 2,439,879 Allen Apr. 20, 1948 2,571,312 Trevaskis Oct. 16, 1951 FOREIGN PATENTS 110,195 Great kBritain of 1917 146,963 Great Britain Oct. 6, 1921 446,124 Great Britain Apr. 24, 19,36 622,780 Germany Nov. 14, 1935 

